Various devices have been invented whereby a screw spindle or threaded support rod is held within a support device telescopically so that the threaded rod or screw spindle is adjustable with respect to the support device quickly by disengaging a threaded interconnection between threads of the rod and threads of the rod-receiving support device; or in a second mode where the threads of the rod are engaged by a threaded "locking" device so that the rod is moved with respect to the support device only by turning the rod for threaded longitudinal movement. Examples of such prior art support mechanisms are found in the Wheelock U.S. Pat. No. 3,603,552 and the Nogler U.S. Pat. No. 3,856,421. In either of these prior art support devices, the locking mechanism is achieved by engagement of the threaded rod with a threaded support device housing portion on one side of the threaded rod and by a movable threaded "locking" member for engagement or disengagement of the rod threads on an opposite side o the threaded rod. The two modes of operation, therefore, permit rapid longitudinal movement of the threaded rod with respect to the support device without rod turning with respect to the support device or permit movement of the threaded rod with respect to the support device when in the locked position only by turning the threaded rod.
A significant problem inherent in support devices such as those disclosed in the above two identified prior art patents is particularly critical in support devices used in the precise machining of workpieces and in machine tools used for intricate manipulations of workpieces that is, vibration of the machinery sometimes causes slight turning of the threaded rod or screw spindle even when the support device is in the "locked" position. The threaded rod support device of the present invention overcomes this problem in the prior art by providing means for engaging one side of the threaded rod against one or more flat, unthreaded, bearing surfaces to prevent any possible unintended longitudinal movement of the threaded rod or spindle with respect to the support device when the device is in a locked mode.